Redox Modulation in Truxene‐Based Phosphaalkenes Through Peripheral Substitution

Peripheral functionalization of the polyaromatic hydrocarbon truxene with low‐coordinate, low‐valent (λ 3 σ 2 ) phosphorus centers in the form of phosphaalkenes provides an effective strategy to induce deplanarization, improve solubility, and introduce pronounced π‐acceptor character. Herein, we report the synthesis of halogenated truxene precursors bearing fluorine and bromine substituents and their stepwise transformation into mono‐, di‐, and triphosphaalkene derivatives. Progressive incorporation of phosphaalkene units leads to a systematic narrowing of the highest occupied molecular orbitals–lowest unoccupied molecular orbitals (LUMO) gap, as evidenced by bathochromic shifts in the low‐energy absorption bands. Electrochemical studies reveal anodically shifted reduction potentials relative to the parent truxene phosphaalkenes, consistent with LUMO stabilization and enhanced electron‐acceptor strength upon peripheral halogenation. Notably, the brominated derivatives reduce at milder potentials relative to their fluorinated counterparts, underscoring a nontrivial electronic modulation of the truxene framework that transcends simple electronegativity arguments. Density functional theory calculations corroborate these experimental trends and provide insight into the underlying structure–property relationships.